The present application is based on and claims priority from Japanese Patent Applications: Hei 11-292304, filed Oct. 14, 1999; 2000-132044, filed May 1, 2000; 2000-132423, filed May 1, 2000; and 2000-243914, filed Aug. 11, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine to be mounted in an electric vehicle.
2. Description of the Related Art
A synchronous electric rotary machine has been adopted to an electric vehicle or a hybrid vehicle because of its high efficiency and high durability. Such a rotary electric machine, which is known as a brush-less DC motor, preferably employs a permanent-magnet-type rotor because of its simple structure.
The output torque of a synchronous machine is proportional to a product of an amount of the armature current of the motor and a magnetic flux density of the magnetic field formed by permanent magnets. The output torque changes in a sinusoidal curve as a phase angle between the direction of the armature current and the direction of the magnetic field changes.
However, in such a synchronous machine used for a vehicle driving motor, if an A-D converter circuit connected between the armature coil and a battery fails to control the terminal voltage of the armature coil, the phase of armature current can not be controlled. Accordingly, the rotation speed of the permanent-magnet-type rotor becomes so high, that a very high output voltage is generated at the armature coil. This requires a smoothing capacitor and other circuits of a control circuit between the armature coil and the battery to provide means for protecting them from such a high voltage. This increases the size and cost of the smoothing capacitor and other circuits.
A main object of the invention is to provide an improved rotary electric machine for driving a vehicle that provide an increased torque without requiring a smoothing capacitor and other circuit to provide means for protecting the circuit elements from a very high voltage.
Another object of the invention is to provide a rotary electric machine that includes a permanent-magnet-type rotor and a induction type rotor which does not require any permanent magnet, whereby a volume of the permanent magnets can be reduced. This prevents such an excessively high output voltage even if an A-D converter circuit fails to control the phase current of the armature winding.
According to a feature of the invention, a rotary electric machine includes a stator core having a plurality of slots disposed equally at an inner periphery, an armature winding disposed in the plurality of slots, and a rotor disposed inside the inner periphery of the stator. The rotor includes a first rotor portion and a second rotor portion disposed magnetically in parallel with the first rotor portion. The first rotor portion has a plurality of permanent-magnet poles, and the second rotor portion has a plurality of salient induction poles. In the above structure, the plurality of permanent magnet poles and the plurality of salient induction poles are shifted from each other to provide a maximum combined output torque.
Preferably, the permanent-magnet poles and the salient induction poles are the same in number. This can combine the output torque of both the first and second rotor portions easily and effectively.
It is also preferable that the salient induction pole is disposed at an angle between 0xc2x0 and 90xc2x0, more preferably between 45xc2x0 and 75xc2x0, in electric angle in advance of the permanent-magnet pole.
According to another feature of the invention, each of the permanent-magnet poles has a permanent magnet inserted in an axially extending magnet hole of the first rotor portion.
According to another feature of the invention, the first rotor portion has as many axially extending arc-shaped slit-groups as the number of the permanent-magnet poles formed at the outer periphery thereof at equal intervals and a plurality of permanent magnets respectively inserted into the arc-shaped slit groups. Therefore, the first rotor portion and the second rotor portion can be formed in the same shape. Preferably, each of the permanent-magnet poles has a pair of permanent magnets inserted at opposite ends of one of the holes. Therefore, it is easy to insert permanents magnet into the holes.
According to another feature of the invention, the rotor includes a magnetic shield member disposed between the first and second rotor portions. Therefore, leakage magnetic flux can be reduced. This increases effective magnetic flux and, ultimately, the output torque.
Another object of the invention is to provide a simple and reliable rotary electric machine whose induced voltage can be controlled by a simple actuator.
According to another feature of the invention, a rotary electric machine includes a permanent-magnet-type rotor having a plurality of magnetic poles and a rotor shaft, a magnetically short-circuit mechanism, disposed near the rotor, for magnetically short-circuiting the magnetic poles. The short-circuiting mechanism includes a short-circuiting member and an actuator for moving the short-circuit member relative to the rotor. The short-circuit member may include a short-circuit plate and a member shaft disposed coaxial with the rotor shaft, and the actuator may be a planetary gear mechanism.
According to another feature of the invention, a rotary electric machine includes a stator having a cylindrical stator core and an armature winding, a cylindrical outer rotor portion disposed inside the stator core, an inner rotor portions disposed inside the outer rotor portion, and a relative angle control mechanism. The outer rotor portion has a plurality of permanent-magnet poles, and the relative angle control mechanism controls relative angular position between the outer and inner rotor portions. Preferably, the inner rotor has a plurality of salient induction poles.